High performance automotive and industrial lubricants are in demand. Accordingly, lubricant manufacturers must provide finished lubricants that exhibit high performance properties. To produce these finished lubricants lubricant manufacturers are seeking higher quality lubricant base oil blend stocks. Performance characteristics that are significant include additive solubility, deposit control, and lubricity.
A growing source of these high quality lubricant base oil blend stocks is synthetic lubricants. Synthetic lubricants include Fischer-Tropsch derived lubricant base oils and polyalphaolefins. Polyalphaolefins are synthetic lubricant base oils produced by a chemical polymerization process. However, these lubricant base oils are expensive to produce. In the search for high performance lubricants, attention has recently been focused on Fischer-Tropsch derived lubricants. Although Fischer-Tropsch derived lubricant base oils are desirable for their biodegradability and low amounts of undesirable impurities such as sulfur, the Fischer-Tropsch derived lubricants generally do not exhibit desirable wear performance, lubricity, and deposit performance. Although it is well known in the art to improve these performance characteristics through the use of additives, these additives are generally expensive and thus, can significantly increase the cost of the lubricant base oil. In addition, engine manufacturers worldwide are considering low sulfur and phosphorus limits on engine oils and additives because it is believed that these limits will provide the safe margins for operation of aftertreatment hardware. Antiwear additives often contain significant amounts of both sulfur and phosphorus. Therefore, it is desirable to produce lubricant base oils with high performance characteristics without the significant use of expensive additives, or with reduced amounts of additives that contain sulfur and phosphorus.
It is well known in the art to produce synthetic lubricants and there have been many developmental attempts at producing synthetic lubricants with high performance characteristics. By way of example, U.S. Pat. No. 6,008,164; U.S. Pat. No. 6,080,301; U.S. Pat. No. 6,165,949; WO 00/14188; WO 02/064710 A2; WO 02/064711 A1; WO 02/070629 A1; and WO 02/070636 A1 are directed to synthetic lubricant compositions and methods for producing the lubricating base stocks.
There has also been research into the properties of hydrocracked base stocks and polyalphaolefins. “The Influence of Chemical Structure on the Physical Properties and Antioxidant Response of Hydrocracked Base Stocks and Polyalphaolefins,” by V. J. Gatto et al., J. Synthetic Lubrication 19-1, April 2002 (19), 3-18, discloses the effect of hydrocracked base stock chemical composition on lubricant properties, oxidation performance, and antioxidant additive response. In this study fifteen hydrocracked base stocks and polyalphaolefins were analyzed.
In spite of the above research into synthetic lubricants, there remains a need for synthetic lubricants comprising Fischer-Tropsch derived lubricant base oils that exhibit high performance including improved friction and wear properties, without requiring the addition of large amounts of additives to achieve this high performance.